Maleated soybean oil derivatives as versatile reactive diluents: Synthesis, characterization, and evaluation

Four maleated soybean oil (SBO) derivatives were synthesized and used as bio‐based reactive diluents (RDs) for alkyd coating systems. The RDs were prepared in a two‐step fashion: (a) Maleation of SBO with maleic anhydride (MA) via an ene reaction followed by (b) a nucleophilic acyl substitution of the grafted succinic anhydride with allyl‐ or methacrylate‐functional molecules. The structures were characterized using 1H NMR, 13C NMR, 13C‐1H heteronuclear single quantum coherence NMR, 13C‐1H heteronuclear multiple bond correlation NMR spectroscopy, FT‐IR (ATR) spectroscopy, and MALDI‐ToF‐MS. The 2D NMR spectroscopy techniques helped confirm that MA was successfully grafted onto SBO. FT‐IR spectroscopy identified new absorption bands at 1780 and 1850 cm−1, following the maleation reaction, corresponding to the anhydride functionality. Alkyd coating formulations were prepared with either 0, 10, 20, or 30 wt% of the different RDs. Brookfield viscosity measurements were conducted on the formulations to measure the efficiency of the SBO‐based RDs. At 20 wt% loading level, the RDs typically reduced the viscosity of the base alkyd resin by 50%–60%. Coatings tests and gel content measurements were also conducted in order to understand the effects that these RDs had on the performance of the alkyd coatings. Vegetable oil‐based reactive diluents were prepared from soybean oil using a simple, scalable, solvent‐free synthetic route. The maleated soybean oil intermediate was characterized by MALDI‐ToF‐MS and 2D NMR spectroscopy techniques for the first time. When these reactive diluents were added to alkyd coatings, they reduced the formulation viscosity without significantly affecting the properties of the crosslinked films. This approach yielded coatings with a high amount of biobased material.